This specification relates to providing inputs to scoring functions. Internet search engines provide information about Internet accessible resources (e.g., Web pages, images, text documents, multimedia content) that are responsive to a user's search query by returning a set of search results in response to the query. A search result includes, for example, a Uniform Resource Locator (URL) and a snippet of information for resources responsive to a query. The search results can be ranked (e.g., in an order) according to scores assigned to the search results by a scoring function.
The scoring function ranks the search results according to various signals, for example, where (and how often) query terms appear in the search results and how common the query terms are in the search results indexed by the search engine. Some scoring functions alternatively, or additionally, use signals that describe past user behavior, for example, how frequently a user selected a given search result after the search result was presented on a search results page for the query.